The present invention relates to DC magnetron sputtering processes and related apparatus. More particularly, the present invention relates to apparatus and processes for high rate, uniform deposition and formation of thin films, such as refractory metals and/or oxides, nitrides, hydrides, carbon-containing compounds and other compounds and alloys of such metals, and also to the deposition and formation of composite films. Because the process and apparatus of the present invention are designed to satisfy the stringent requirements of optical coatings, they are applicable as well to a number of other coating applications having less rigorous requirements.